Non-aqueous homogenous biocatalytic conversion of polysaccharides in ionic liquids using chemically modified glucosidase

Abstract

The increasing requirement to produce platform chemicals and fuels from renewable sources means advances in biocatalysis are rapidly becoming a necessity. Biomass is widely used in nature as a source of energy and as chemical building blocks. However, recalcitrance towards traditional chemical processes and solvents provides a significant barrier to widespread utility. Here, by optimizing enzyme solubility in ionic liquids, we have discovered solvent-induced substrate promiscuity of glucosidase, demonstrating an unprecedented example of homogeneous enzyme bioprocessing of cellulose. Specifically, chemical modification of glucosidase for solubilization in ionic liquids can increase thermal stability to up to 137 °C, allowing for enzymatic activity 30 times greater than is possible in aqueous media. These results establish that through a synergistic combination of chemical biology (enzyme modification) and reaction engineering (solvent choice), the biocatalytic capability of enzymes can be intensified: a key step towards the full-scale deployment of industrial biocatalysis.

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Fig. 1: Mechanisms of cellulase activity.
Fig. 2: Structure of glucosidase in ionic liquids.
Fig. 3: Stability of glucosidase in ionic liquids.
Fig. 4: Glucosidase in the reaction medium.
Fig. 5: Enzyme activity in pure ionic liquid.

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Acknowledgements

The authors thank the EPSRC (Frontier Engineering Grant EP/K038648/1) for financial support. The authors also thank G. Siligardi, R. Hussain and T. Jaforvi at the Diamond Light Source for access to the B23 beamline, N. Terrill and A. Smith at the Diamond Light Source for access and support at the I22 beamline, W.-C. Tu for running HPLC samples and P. Carry for access to FTIR and dynamic light scattering.

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A.P.S.B. designed and performed the experiments, A.P.S.B. and J.P.H. wrote the manuscript, and L.B.-L. synthesized and characterized the ionic liquids. All authors discussed the results and commented on the manuscript.

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Correspondence to Jason P. Hallett.

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The authors declare no competing interests.

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Brogan, A.P.S., Bui-Le, L. & Hallett, J.P. Non-aqueous homogenous biocatalytic conversion of polysaccharides in ionic liquids using chemically modified glucosidase. Nature Chem 10, 859–865 (2018). https://doi.org/10.1038/s41557-018-0088-6

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